Release v0.1.29

Changes

• Fix typo in DEVELOPER.md, submitted by @billykern
• Improve and cleanup the Windows and PyCharm build process
• Update build system to use poetry.core, submitted by @Spectre5
• Fix the GitHub test suite by adding Python version into cache id
• Update isort to use the new black profile, submitted by @Spectre5
• Move to newer versions of various build dependencies (black, Sphinx, etc.)
• Standardize on UNIX line endings in Git working copy and PyPI package
• Make improvements to Read the Docs integration, including a PR merge gate
• Clean up badges shown in documentation, so they are links to something sane
• Make improvements to the MyPy and Pylint configuration
• Move to a new two-step release process based on cedar-backup3
• Create a changelog for the first time, along with new release process